1. Field of the Invention
This invention relates to a process for preparing a phenyl eser and/or phenol by reacting benzene, a carboxylic acid and molecular oxygen. This invention also relates to a new catalyst for the reaction.
2. Description of the Prior Art
The preparation of a phenyl ester and/or phenol from benzene, a carboxylic acid and molecular oxygen in the gas or liquid phase in the presence of a catalyst containing a noble metal of Group VIII of the periodic table, especially palladium, is known. It is also known that the catalytic activity can be improved by adding a weak acid salt of a strong base, such as an alkali metal salt of a carboxylic acid, as an auxiliary activator. It has been proposed to add a promotor such as gold, silver, copper, iron manganese or the like, which is not effective alone, to the palladium catalyst, in order to promote catalytic activity. The amount of the promotor is preferably a maximum of 50 atomic percent of palladium. (Japanese Patent Publication No. 33024/1971 ). It is also known that a carboxylic acid salt of a metal of Group IIb, III or IV of the periodic table is effective as an activator and a metal of Group Vb and VIb, especially tellurium or bismuth, is effective as a promotor. The amount of the promotor to precious metal is a maximum of 60 atomic percent, preferably 20-40 atomic percent. (British Patent No. 1,200,392 and British Patent No. 1,200,708). However, the known catalysts for preparing a phenyl ester from benzene, carboxylic acid and molecular oxygen, do not have enough catalytic activity for an industrial operation. Since an expensive noble metal, such as palladium, is used, there is a need for increasing catalytic activity per weight of palladium. The known catalysts have a further disadvantage of decreased catalytic activity in a short time in the gas phase reaction.